Study of prototypical Diels-Alder reactions by a hybrid density functional/Hartree-Fock approach

1996 ◽  
Vol 251 (5-6) ◽  
pp. 393-399 ◽  
Author(s):  
Vincenzo Barone ◽  
Roger Arnaud
Keyword(s):  
Density Functional ◽  
Diels Alder ◽  
Hartree Fock ◽  
Hybrid Density Functional

scholarly journals The crystalline structure of SrRuO3: Application of hybrid scheme to the density functionals revised for solids

2017 ◽  
Vol 57 (2) ◽  
Author(s):  
Šarūnas Masys ◽  
Valdas Jonauskas
Keyword(s):  
Crystalline Structure ◽  
Density Functional ◽  
Theoretical Modelling ◽  
Density Functionals ◽  
Hybrid Scheme ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Hartree Fock ◽  
Hybrid Density Functional ◽  
Theory Scheme

The crystalline structure of ground-state orthorhombic SrRuO3 is reproduced by applying the hybrid density functional theory scheme to the functionals based on the revised generalized-gradient approximations for solidstate calculations. The amount of Hartree–Fock (HF) exchange energy is varied in the range of 5–20% in order to systematically ascertain the optimum value of HF mixing which in turn ensures the best correspondence to the experimental measurements. Such investigation allows one to expand the set of tools that could be used for the efficient theoretical modelling of, for example, only recently stabilized phases of SrRuO3, helping to resolve issues emerging for the experimentalists.

Prediction of the photoelectron spectrum for XPY2 (X = H, F, Cl; Y = O, S) type of molecules by ab initio and DFT methods

2006 ◽  
Vol 84 (1) ◽  
pp. 5-9 ◽  
Author(s):  
Didier Bégué ◽  
Jean-marc Sotiropoulos ◽  
Claude Pouchan ◽  
Daisy Y Zhang
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Radical Cations ◽  
Dft Methods ◽  
Functional Theory ◽  
Hartree Fock ◽  
Orbital Energies ◽  
Koopmans Theorem ◽  
Vertical Ionization Potentials ◽  
Hybrid Density Functional

The present study reports the theoretical vertical ionization potentials (IPs) for all the valence electrons in six XPY2 molecules by utilizing the corrected orbital energies calculated with three theoretical methods, namely, the ab initio Hartree–Fock (HF), and both the pure and hybrid density functional theory (DFT) methods at, respectively, the BLYP/6-311+G* and B3lYP/6-311+G* levels of theory. Evaluation of the numerical corrections to the orbital energies was achieved by comparisons with the IP values obtained via explicit computation of the energy differences between the neutral molecules and the corresponding radical cations (the ΔSCF method) and shows values from –0.9 to –1.9 eV for the HF, and positive values from 2.9 to 3.9 eV and from 1.8 to 2.4 eV for the pure and hybrid DFT methods, respectively. In contrast to the orbital energies, the ΔSCF method is shown to give consistent values among the three methods, as well as reasonable agreement with the experimental IP values.Key words: ionization potential, phosphorane, Koopmans' theorem, Janak's theorem.

A Study of Reactivity of Model Compounds of Lignin Biopolymer

2021 ◽  
Vol 316 ◽  
pp. 75-80
Author(s):  
Oleg Kh. Karimov ◽  
Galina Yu. Kolchina ◽  
Eldar M. Movsumzade
Keyword(s):  
Aromatic Ring ◽  
Quantum Chemical ◽  
Density Functional ◽  
Nucleophilic Attack ◽  
Hydroxyl Group ◽  
Model Compounds ◽  
Hartree Fock ◽  
Quantitative Characteristics ◽  
Derivatives Of ◽  
Hybrid Density Functional

In the framework of method of the B3LYP hybrid density functional and the restricted Hartree-Fock method, quantum-chemical calculations of model compounds of lignin, i.e. derivatives of p-hydroxycinnamic alcohol were carried out. The structures and reactivity of coumaric, coniferyl and synapol alcohols were studied. Quantitative characteristics of the reactivity of these acids are given. It is found that the electronic structure of lignin is determined primarily by the charge distribution in its structural phenylpropane unit. In the molecules of all model compounds of lignin, the center for nucleophilic attack is the carbon of aromatic ring (E-ring) with a hydroxyl group, and in the molecule of synapol alcohol, this center is also the carbon of the aromatic ring (E-ring) with a methoxy group. In all three compounds, a center with an increased electron density appears on the Сβ carbon atom.

ELEMENTAL AND MIXED ACTINIDE DIOXIDES: AN AB INITIO STUDY

2012 ◽  
Vol 11 (03) ◽  
pp. 611-629 ◽  
Author(s):  
LI MA ◽  
RAYMOND ATTA-FYNN ◽  
ASOK K. RAY
Keyword(s):  
Density Functional ◽  
Band Gaps ◽  
Qualitative Description ◽  
Functional Theory ◽  
Magnetic Structures ◽  
Lattice Constants ◽  
Hartree Fock ◽  
Ground State Structures ◽  
Hybrid Density Functional ◽  
Theoretical Results

We present a systematic study of the electronic, geometric, and magnetic properties of the actinide dioxides, UO2 , PuO2 , AmO2 , U0.5Pu0.5O2 , U0.5Am0.5O2 and Pu0.5Am0.5O2 . For UO2 , PuO2 and AmO2 , both density functional and hybrid density functional theory (DFT and HDFT) have been used. The fractions of exact Hartree–Fock (HF) exchange chosen were 25% and 40% for the hybrid density functional. For U0.5Pu0.5O2 , U0.5Am0.5O2 and Pu0.5Am0.5O2 , only HDFT with 40% exact HF exchange was used. Each compound has been studied at the nonmagnetic, ferromagnetic and anti-ferromagnetic configurations, with and without spin–orbit coupling (SOC). The lattice parameters, magnetic structures, bulk moduli, band gaps and density of states have been computed and compared to available experimental data and other theoretical results. Pure DFT fails to provide a satisfactory qualitative description of the electronic and magnetic structures of the actinide dioxides. On the other hand, HDFT performs very well in the prediction and description of the properties of the actinide dioxides. Our total energy calculations clearly indicate that the ground-state structures are anti-ferromagnetic for all actinide dioxides considered here. The lattice constants and the band gaps expand with an increase of HF exchange in HDFT. The influence of SOC is found to be significant.

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